The activity level of calcium-dependent proteases of the calpain family in skeletal muscles of the atlantic salmon (Salmo salar L.) and brown trout (Salmo trutta L.) from some watercourses (the Zolotitsa River and Lopatka stream) draining to the White Sea (arkhangelsk region) was estimated. a correlation between length-weight parameters of the fish and the rate of calcium-dependent proteolysis in their skeletal muscles was demonstrated. atlantic salmon parr from the Zolotitsa River were larger and had a higher growth rate compared to salmon of the same age from rivers of the Murmansk Region. The comparison of length-weight parameters and data on the rate of calcium-dependent proteolysis
in brown trout parr from three watercourses draining to the White Sea and Lake Onegorev ealed the lowest growth rate in fish aged 3+, 4+ from the Lopatka stream. The obtained results indicate that the growth rate of salmonids S. salar and S. trutta depends on the environmental condition and availability of food resources in the studied waters.